Er... the setbacks pertain to the tired MD vs DO debate. And it's difficult to quantify how hard it is to become a specialized surgeon as DO. This depends on matching into a competitive surgical residency which in turn depends on clinical year performance, USMLEs (MD residencies don't care about COMLEX), good letters etc
With good USMLE scores, you can certainly become a general surgeon. Fellowships are possible thereafter with a strong residency performance at an academic center.